Run tests only with current stable toolchain

This saves a bit of execution time.
There's no point in running MSRV and stable, because there shouldn't be
a difference. So we opt for stable because it tends to be faster.

Signed-off-by: Matthias Beyer <[email protected]>

.github/workflows/msrv.yml

@@ -29,26 +29,19 @@ jobs:
   test:
     name: Test Suite
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        rust:
-          - 1.70.0
-          - 1.73.0 # stable
-          - beta
     steps:
       - name: Checkout sources
         uses: actions/[email protected]
 
       - name: Install toolchain
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: ${{ matrix.rust }}
+          toolchain: 1.73.0
 
       - name: Cache
         uses: Swatinem/rust-cache@v2
 
       - name: Run cargo test
-        continue-on-error: ${{ matrix.rust == 'beta' }}
         run: cargo test --all-features
 
   fmt: